Select all in output area selects entire page text

notebook 5.7.8
ipython 7.5.0
Firefox 67.0
macOS

In output cell area, select all selects all the text on the entire page window.

**Expected:** select all in output area selects just the output text
like it does currently in cells

Reproduce the issue in a Jupyter Notebook output cell using the reported Firefox and macOS context, then compare Select All behavior with a notebook code cell. Done means selecting all within the output area selects only the output text rather than text across the page.

Written by the indexing model from the issue text.